The present invention relates to an apparatus for and a method of, selectively playing back a plurality of optical discs having different numbers of recording layers and/or different positions of recording layers along the thickness of the optical discs, with a device for determining the type of an optical disc which has been loaded.
Compact discs (hereinafter referred to as CD-DA (CD-DIGITAL AUDIO) are presently in widespread use, and DVDs (Digital Versatile Discs) have been proposed as new optical discs having a greater capacity than the CD-DA.
A DVD is optical disk having a diameter of 12 cm with information recorded at a track pitch of 0.8 xcexcm which is one half of the related art CD track pitch of 1.6 xcexcm, in a high density of about 4 Gbytes on one surface by a semiconductor laser whose wavelength has been changed to 650 nm, for example, from 780 nm for CDs, according to an improved modulation process of the EFM (Eight to Fourteen Modulation) employed for CDs.
Based on the above DVD specifications, there has also been developed a multilayer disc having two layers as recording layers.
Since disks of various types such as CD-DA and DVD are present in the market, playback apparatus are required to play back those discs of various types.
Playback apparatus that are compatible with various types of discs need to change laser wavelengths and decoding schemes depending on the type of a disk to be played back. Therefore, when a disc is loaded into a playback apparatus, it is necessary for the playback apparatus to determine the type of the disc.
The type of a disc can be determined by reading management information, e.g., TOC, from the disk. However, such a process is problematic in that it is time-consuming to determine the disc type.
For example, a playback apparatus having a CD-DA pickup and decoding system and a DVD pickup and decoding system carries out a start-up process for laser beam application and servo control with one of the pickups because the type of a loaded disc is unknown, and then reaches a condition capable of reading data for reading TOC data. If the type of the loaded disc and the used pickup do no match each other, then it is necessary to change to the other pickup for a start-up process for laser beam application and servo control. Therefore, it takes a certain time until the TOC data can be read.
For the reasons described above, if it takes a certain time to determine the type of a disc when the disc is loaded, then the user has to wait a long period of time before the disk actually starts to be played back.
Some sensor mechanism may be provided to determine the type of a disc when the disc is loaded. However, the addition of such a sensor mechanism presents an obstacle to efforts to simplify the structure of the playback apparatus and reduce the cost thereof.
It is an object of the present invention to be able to determine the type of a disk quickly when the disk is loaded without the need for special components such as a sensor mechanism or the like.
According to the present invention, there is provided an apparatus for selectively playing back a plurality of optical discs having different numbers of recording layers and/or different positions of recording layers along the thickness of the optical discs, including applying a device for applying a light beam to a loaded optical disc, a photodetector device for detecting reflected light from the optical disc upon application of the light beam from the applying device, a signal generator for generating a signal based on the reflected light detected by the photodetector, a detector for detecting the number of peaks of the signal generated by the signal generator and timings at which the peaks are outputted, a deciding device for determining the type of the loaded optical disc based on the detected number of peaks and/or the detected timings, and a setting device for setting a playback condition depending on the type of the loaded optical disc determined by the deciding device.
According to the present invention, there is also provided an apparatus for selectively playing back a first optical disc having a single recording layer and a second optical disc having a plurality of recording layers, including an applying device for applying a light beam to a loaded optical disc, a photodetector for detecting reflected light from the optical disc upon application of the light beam from the applying device, a signal generator for generating a signal based on the reflected light detected by the photodetector, a detector for detecting the number of peaks of the signal generated by the signal generator and timings at which the peaks are outputted, a deciding device for determining the type of the loaded optical disc based on the detected number of peaks and/or the detected timings, and a setting device for setting a playback condition depending on the type of the loaded optical disc determined by the deciding device.
According to the present invention, there is further provided a method of selectively playing back a plurality of optical discs having different numbers of recording layers and/or different positions of recording layers along the thickness of the optical discs, including the steps of applying a light beam to a loaded optical disc, detecting reflected light from the optical disc upon application of the light beam, generating a signal based on the reflected light which is detected, detecting the number of peaks of the generated signal and timings at which the peaks are outputted, determining the type of the loaded optical disc based on the detected number of peaks and/or the detected timings, and setting a playback condition depending on the type of the loaded optical disc determined by the decision means.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.